This invention is directed to nets in general and, more specifically, to shrimp trawls. Shrimp are a small decopod crustacean. They live on the bottom of the ocean and tend to inhabit sandy coast bottom. They are usually caught by fishing for them with what is called a shrimp trawl. This is a type of net that is pulled across the bottom of the water body being fished. The trawl is attached to a boat by towlines. The trawls can be pulled at any speed; faster speeds produce more shrimp, although faster speed is not an absolute necessity to catching shrimp.
The trawl is open at one end; as the trawl is being towed across the bottom, shrimp are entrapped in the trawl. The trawl is usually a wide funnel-shaped net in which the open end is kept open by some type of frame work or other means.
It can be seen that a net that is pulled across the sea bottom would tend to receive a great deal of abuse. For example, the trawl can be dragged across sharp objects which may be buried in the substrate. This could, and in actual practice does, cause damage to the trawl which requires the fisherman to remove the trawl from service and have it repaired, a process which could be time consuming and expensive.
Also, because of the inherent nature of this type of shrimping, i.e. dragging the trawl across the ocean bottom, it can easily be seen that friction exists between the trawl and the ocean substrate. This friction also decreases the longevity of the trawl and increases the force with which the trawl must be pulled, thereby increasing the useage of motor fuel on the part of the boat.
Some of the prior art has dealt with the problem of trawl fishing. U. S. Pat. No. 4,381,617 is directed to a device for reducing the friction of a bottom contacting fishnet by enclosing the leadline of the net with a flexible bearing means which can be a tube of flexible polyethylene film. The film serves as a bearing surface for the leadline as it is dragged across the substrate.
U. S. Pat. No. 3,023,529 is directed to a trawl net which is provided with riblines to which are attached chafing gear strips which, according to the disclosure, tends to reduce friction between the trawl and the bottom substrate.
Also, U. S. Pat. No. 4,299,047 tends to solve the friction problem by providing wheels to a beam trawl.
There exist two types of trawl net structures that are used in shrimping. There is the beam trawl in which the mouth of the trawl net is kept open by some type of frame work. Also, there is the other trawl in which a device known as the trawl door, which is sometimes referred to as an otter door, serves to keep the net open and to keep the bottom close to the substrate by adjusting the angle of the trawl door as the trawl is being pulled across the ocean bottom. In any event, whatever type of trawl net is used, abuse and wear is inflicted to the net to the extent that the net can be rendered useless, i.e. the loss of shrimp and/or the loss of the net. As mentioned previously, the trawl must be taken out of service and materials and labor must be expended to repair the trawl. This repair can take a considerable amount of time.